Protective sleeving is used throughout the automotive, marine and aerospace industries to organize and protect elongated items, such as wiring harnesses and optical fiber cables. The sleeving surrounds the elongated items and protects them against cuts, abrasion, radiant heat, vibration induced wear and other harsh environmental threats. When positioned within protective sleeving, the wiring or cables are also held together in a neat bundle, allowing a multiplicity of different items to be handled like a sub-assembly, thus saving time and effort during integration of the items into a product.
Protective sleeving may be made by weaving filaments into a substrate and then resiliently biasing the substrate into a tubular form to define a central space for receiving the elongated items. Biasing may be effected by various means appropriate to the types of yarns used to make the substrate. Polymer filaments may be biased by heating them when the substrate is wrapped about a cylindrical mandrel, the filaments taking a permanent set conforming to the shape of the mandrel. Filaments can also be resiliently biased into a curved shape by chemical means as well as by cold working.
When substrates are biased into a tubular shape, monofilaments are typically oriented in the “hoop” or circumferential direction of the tube. Monofilaments provide excellent stiffness and strong resilient biasing that maintains the substrate in the tubular shape and tends to restore the substrate to this shape in the absence of distorting forces such as occur when the sleeve is manipulated to insert or remove an elongated item.
A significant disadvantage associated with sleeves that are biased into a tubular shape is that the biasing is effected by a separate step in the process of making the sleeve. The filaments comprising the sleeve may be biased by cold working before weaving or may be biased after weaving by heating the substrate when wrapped about a mandrel, but these actions constitute a separate step that adds to the cost and the time required to produce the sleeve. It would be advantageous to provide a sleeve formed from a substrate that is self-curling and needs no separate step to effect resilient biasing of the filaments into the tubular shape.